1. Field of the Art
This invention relates to a turning zigzag embroidery machine, which is suitable, for example, for reproducing an embroidery design or pattern with turning zigzag figures according to given stitch data.
2. Technical Background
Generally, so-called turning zigzag sewing machines, which can serve for the turning zigzag embroidering, have been known in the art, for instance, from Japanese Laid-Open Patent Application 63-203188. The conventional turning zigzag embroidery machine of this sort is usually composed of a base table adapted to hold a lower embroidering thread in position, an embroidery machine head located above the base table and adapted to reciprocate an embroidering needle with an upper thread up and down at a confronting position relative to the lower thread while simultaneously rocking the embroidering needle across a given width, a movable frame located movably on the base table under the embroidery machine head and driven from a drive source for movements in sideward directions and in forward and backward directions (in the directions of x- and y-axes) on the base table, and a rotatable frame adapted to hold embroidering cloth in a stretched state within the movable frame and to be turned together with the embroidering cloth within the movable frame by a rotational drive source provided on the movable frame.
With a conventional turning zigzag sewing machine of this sort, as the embroidering needle on the head of the embroidery machine is put in rocking movement across a certain rocking width or widths simultaneously with reciprocating movement, the movable frame is driven in the directions of x- and y-axes and the embroidering cloth is turned together with the rotatable frame on the movable frame to advance the embroidering needle from one stitch point to another. By repeating such a needle advancing action, an embroidery pattern with a turning zigzag figure or figures is reproduced on the cloth according to the rocking width of the embroidering needle. An embroidery machine of this sort has an advantage that even complicated embroidery patterns can be formed in a relatively short period of time.
The turning zigzag sewing machines of the sort mentioned above usually includes a position sensor for detection of displacements of the movable frame in the directions of x- and y-axes, a rotational angle sensor for detection of rotational angles of the rotatable frame relative to the movable frame, and a rocking width sensor for detection of the rocking width of the embroidering needle, in order to reproduce an embroidery pattern according to a prior teaching operation or the so-called "exemplary learning" prior to an actual operation.
More specifically, in a prior teaching operation, a skilled operator makes adjustments of the rocking width of the reciprocating embroidering needle while at the same time manually moving or turning the movable and rotatable frames to simulate the motions which are necessary to produce a desired embroidery pattern. At this time, the signals from the respective sensors are read in so as to store the necessary positional data of the center of the rotatable frame relative to the center of the embroidering needle, including the position of the movable frame (or the center of the rotatable frame), the rotational angle of the rotatable frame, and the rocking width of the embroidering needle. Thereafter, the above-mentioned drives for the movable and rotatable frames are operated according to the stored data to reproduce the embroidery pattern repeatedly in the same manner as by a skilled operator.
In case of the above-described prior art turning zigzag embroidery machine, however, the embroidery machine head as well as the drives for the movable and rotatable frames are operated according to the so-called teaching data which are input by a skilled operator in a prior teaching operation. Therefore, the conventional embroidery machine is capable of simple reproductions of an embroidery pattern as learned through a teaching operation, but it is incapable of scaling up or down the size of or altering the design of am embroidery pattern or changing its position when it is desired to reproduce the pattern in a more improved quality.
In this connection, the applicants proposed in their prior patent application, Japanese Patent Application 4-232853, a stitch data preparation device (hereinafter referred to as "the prior art") which is provided with arithmetic conversion means to convert the data of the center of the rotatable frame relative to the center of the embroidering needle, as learned from a teaching operation including the rotational angle of the rotatable frame and the rocking width of the embroidering needle, into data of the center of the embroidering needle relative to the center of the rotatable frame, and to scale up or down or to alter an embroidery pattern on the basis of the arithmetically converted data.
According to the stitch data preparation device of the prior art, the data of an embroidery pattern, which has been enlarged or reduced in size or altered in shape on the basis of the data of the embroidering needle center relative to the rotatable frame center, are stored in a memory medium like a floppy disk to supply the edited data to the outside as output data. Therefore, the output data of the prior art device, based on the needle center, would be unable to operate a turning zigzag sewing machine even if they could be loaded on the sewing machine.
Further, if it may be possible to add data of the rotational angle and rocking width, for example, at the time of preparing stitch data by entering stitch points on a pattern input device like a tablet, to obtain needle center data which are easily editable to scale up or down or to alter an embroidery pattern design. However, this data exclusively consists of needle center data, so that they are unable to operate conventional turning zigzag sewing machines, failing to utilize the data entered through a tablet or a similar pattern input device.
In view of the above-discussed problems of the prior art, the present invention has as its object the provision of a turning zigzag embroidery machine which is capable of reading in needle center data, a data format which permits data editing for scaling up or down an embroidery pattern or for other purposes, and arithmetically converting the input data into a format which can control the operations of the embroidery machine head and the movable and rotatable frame drives to reproduce an embroidery pattern which is improved in quality.